Mechanical embossing texture differentiation between chemically restricted areas and non-restricted areas

ABSTRACT

Disclosed is a method of manufacturing a mechanically and chemically embossed surface covering having selectively textured surfaces. The method includes forming a web coated with a wear layer. The coated web is heated to a temperature at which the wear layer is cured, the foam layer expands, and the pattern is chemically embossed to form a surface covering having foamed regions and nonfoamed regions. The temperature gradient of the surface covering is adjusted such that there is a temperature gradient difference between the foamed and nonfoamed regions. A surface texture is then mechanically embossed into the wear layer and selectively set onto the wear layer substantially overlying the non-foamed regions.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 09/789,172,filed on Feb. 20, 2001 now U.S. Pat. No. 6,613,256.

FIELD OF THE INVENTION

The present invention relates generally to surface coverings. Inparticular, the invention relates to a mechanically and chemicallyembossed surface covering having a selectively textured surface.

BACKGROUND

Decorative laminate surface coverings can be formed into sheets orindividual tiles. Typically, in the manufacture of a resilient floorcovering, a wear layer is combined with a substrate and resin to formthe resilient sheet or tile. The substrate usually comprises a felted ormatted fibrous sheet of overlapping, intertwined filaments or fibers. Asubstantially uniform layer of a liquid or semi-liquid resinouscomposition containing a synthetic polymeric material, usually anungelled polyvinyl chloride plastisol and a blowing or foaming agent istypically applied to the substrate. The liquid or semi-liquid plastisolvinyl resin composition is subsequently firmed or gelled at an elevatedtemperature. This gelled plastisol may be printed with a decorativepattern or design having a blowing or foaming inhibitor for chemicallyembossing the substrate.

Decorative laminate surface coverings are often designed to havetextured surfaces patterned to duplicate a look of actual wood, tile,brick, stone, and other such products. Typically, the texture is eithermechanically embossed by pressing a pattern into the surface covering orchemically embossed by using foam retarding agents to restrict expansionof a foamable layer in specific regions of the design. Although thesemethods provide attractive decorative surface coverings, they arelimited in their capability to replicate the appearance of the actualproduct.

There continues to be a demand by consumers for surface coverings thathave a “more realistic” appearance to the natural product. U.S. Pat. No.5,961,903 describes one method of manufacturing an embossed resinousfoam product which is both chemically and mechanically embossed, andincludes forming a foamable, resinous composition which contains ablowing agent. An ink composition having a blow modifying agent/retarderis printed onto the foamable, resinous composition. A wear layer isapplied and the wear layer/foamable composition is heated to expand thefoam and cure the wear layer. Areas of the foam printed with theprinting ink composition are restricted from expanding resulting in achemically embossed product. The chemically embossed structure is cooledto ambient temperature before any further handling. Thereafter, thechemically embossed product is reheated and a texture is mechanicallyembossed, using an overall textured embossing roll, into the hot wearlayer overlying the non-restricted/up foam regions by pressure while itis relatively soft, plastic, and moldable. After the foam ismechanically embossed and has cooled to ambient temperature, a wearlayer is coated and cured onto the chemically and mechanically embossedfoam.

An alternative method for making a chemically and mechanically embossedsurface covering (Armstrong U.S. Ser. No. 09/770,582 incorporated in byreference), includes coating a backing layer with a foamable layer, andadding a print layer to it. The print layer forms a design and a portionof the design is formed with a retarder composition. A thermoplasticwear layer is applied onto the print layer and cured by heat at atemperature sufficiently high enough to expand the foamable layer. Theareas of the design layer where the retarder composition is applied arealso chemically embossed during such curing. In a continuous process andwithout cooling to ambient conditions, the temperature of the curedthermoplastic wear layer is adjusted by heating, and the wear layer isthen mechanically embossed to have a surface texture in the wear layeroverlying the unrestricted/up areas. Optionally, a top coat can beapplied to the wear layer before curing and expanding the foam, and thetop coat can be mechanically embossed.

Despite existing methods of making chemically and mechanically embossedsurface coverings, there is a need for a surface covering having achemically embossed foam layer and a selectively textured top coat wearlayer for simulating a natural product.

SUMMARY

Briefly described, the present invention comprises a method ofmanufacturing a mechanically and chemically embossed surface covering.In one embodiment of the present method, a mechanically and chemicallyembossed surface covering is made comprising forming a web having asubstrate, an expandable foam layer, and at least one inhibitor/retarderor activator composition disposed as a pattern proximate the foam layer.The web is coated with a wear layer to form a coated web. The coated webis heated to a temperature at which the wear layer is cured, the foamlayer expands, and the pattern is chemically embossed to form a surfacecovering having foamed regions and nonfoamed or restricted regions. Thetemperature gradient of the surface covering is adjusted such that thereis a difference between the foamed and non-foamed regions. At least onesurface texture is mechanically embossed onto the wear layer with thesurface texture being predominantly set onto the wear layer, whichsubstantially overlies the nonfoamed regions.

In greater detail, the surface covering is subjected to an overalltextured mechanical embossing roll nip. In one embodiment the embossingroll can have two or more different textures. The temperature gradientis adjusted such that the wear layer over the nonfoamed or restrictedregions is mechanically textured, and the wear layer over the foamedregions is substantially non-textured. The surface texture is set intothe wear layer residing predominantly over the nonfoamed regions.

Another aspect of the present invention relates to a method ofmanufacturing a mechanically and chemically embossed surface coveringcomprising a top coat. The method includes forming a web comprising asubstrate, a curable wear layer, and an expandable foam layer betweenthe substrate and the wear layer. Additionally, at least one inhibitoror activator composition is disposed on the covering as a patternproximate the foam layer. The wear layer of the web is coated with across-linkable top coat to form a top coated web. The top coated web isheated to a temperature at which the top coat is substantiallycross-linked and cured, the wear layer is cured, the foam layer expands,and the pattern is chemically embossed to form a surface covering havingfoamed and nonfoamed regions. The temperature gradient of the surfacecovering is adjusted such that there is a difference between the foamedand non-foamed regions. At least one surface texture is mechanicallyembossed onto the wear layer and the surface texture is predominantlyset into the wear layer substantially overlying the nonfoamed regions.

A further aspect of the present invention relates to a method ofmanufacturing a mechanically and chemically embossed surface covering byback heating the covering. The method includes forming a web comprisinga substrate, an expandable foam layer, and at least one inhibitorcomposition disposed as a pattern proximate the foam layer, and coatingthe web with a wear layer to form a coated web. The coated web is thenheated to a temperature at which the wear layer is cured, the foam layerexpands, and the pattern is chemically embossed to form a surfacecovering having foamed regions and nonfoamed or restricted regions. Heatis then applied to the substrate side of the surface covering or thebackside of the covering. The resulting face temperature of thesubstrate side is greater than that of the wear layer. At least onesurface texture is mechanically embossed onto the wear layer. Thesurface texture is set into the wear layer areas residing predominantlyover the nonfoamed or restricted regions of the surface covering.

Furthermore, there is included a chemically and mechanically embossedsurface covering. The surface covering comprises a substrate and a foamlayer disposed on the substrate. The foamed layer has a chemicallyembossed pattern having foamed regions and non-foamed or restrictedregions imposed thereon. “Foamed regions” correspond to “up areas” ofthe chemical embossing, and the “non-foamed regions correspond to the“down areas” of the chemical embossing. Although no foaming is preferredin the “down areas” to impart the deepest chemical embossing effect,some amount of foaming (partial foaming) may occur in the “non-foamedregions” dependent upon chemical embossing conditions. Therefore,“non-foamed regions” also include partial foamed regions as long as theyimpart a chemical embossing effect. A wear layer is disposed on thefoamed layer, and a surface texture mechanically embossed andselectively set into the wear layer areas residing predominantly overthe non-foamed or restricted regions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an embodiment of a process ofmanufacturing a mechanically and chemically embossed surface covering;

FIG. 2 is a schematic view of another embodiment of a process ofmanufacturing a mechanically and chemically embossed surface covering ofthe present invention;

FIG. 3 is a partial cross sectional and elevation view of an embodimentof a mechanically and chemically embossed surface covering made inaccordance with the process of FIG. 1; and

FIG. 4 is a partial cross sectional and elevation view of an embodimentof a mechanically and chemically embossed surface covering made inaccordance with the process of FIG. 2.

DETAILED DESCRIPTION

The present invention comprises a method of manufacturing a mechanicallyand chemically embossed surface covering. The method of manufacturing amechanically and chemically embossed surface covering can compriseforming a web having a substrate, an expandable foam layer, and at leastone inhibitor/retarder or activator composition disposed as a patternproximate the foam layer. The web may be coated with a wear layer toform a coated web. Additionally, a top coat may also be added. Thecoated web is heated to a temperature at which the wear layer is cured,the foam layer expands, and the pattern is chemically embossed to form asurface covering having foamed and nonfoamed regions. The temperaturegradient of the surface covering is adjusted such that there is adifference between the foamed and non-foamed regions. At least onesurface texture is mechanically embossed onto the wear layer with thesurface texture being predominantly set onto the wear layer, whichsubstantially overlies the nonfoamed regions.

Additionally, after adjusting the temperature gradient of the surfacecovering, the covering is then subjected to an overall texturedmechanical embossing roll nip which can have regions of more than onetexture. The temperature gradient is adjusted such that the wear layerover the nonfoamed or restricted regions is mechanically textured, andthe wear layer over the foamed regions is substantially non-textured.The surface texture is set onto the wear layer residing predominantlyover the nonfoamed regions.

In another embodiment, the temperature gradient is adjusted so that theembossing texture is predominately set onto the wear layer overlying theunfoamed regions and partially set into the wear layer overlying thefoamed regions.

In yet another embodiment, the temperature gradient can be adjusted, andan embossing roll with at least two regions of different texture can beused to set a first texture into the wear layer overlying the nonfoamedregions and a second texture into the wear layer overlying the foamedregions.

Additionally, in another embodiment, the chemical embossed surfacecovering having mechanical embossing set predominately into the wearlayer overlying the unfoamed regions can be reheated, temperaturegradients adjusted, and a second embossing texture set predominatelyinto the wear layer overlying the foamed regions. In fact, we havediscovered that temperature gradients can be controlled that allows thewear layer overlying the foamed and nonfoamed regions to beindependently predominately textured. For example, the wear layeroverlying the foamed regions can be predominately textured first, andsubsequently the wear layer overlying the unfoamed regions can bepredominately textured.

The temperature gradient is the rate of change in temperature from topto bottom within the surface covering. For example, if the surfacecovering is sliced 1mil at a time, each 1 mil layer would have atemperature. This difference between the temperature of each slice wouldbe the rate of change of temperature (or temperature gradient) for thatregion. Alternatively, the temperature gradient may be described as atemperature profile from top to bottom in the specific regions of thesurface covering. The specific regions may include the foamed andunfoamed regions of the surface covering.

In the case where the embossed texture is set into the wear layer or topcoat, the temperature gradient or profile of the surface covering issuch that when the wear layer/top coat comes in contact with theembossing roll it can cool quickly and “set” the embossing. If thetemperature of the surface is higher than the back temperature, there isa temperature gradient through the sample due to thermal conductivityand heat capacity of the materials (heat flow). In this case, the heatflow (temperature gradient/profile) would be from face to back. If thetemperature is higher on the back, then the heat flow (temperaturegradient/profile) would be from back to face.

“Foamed regions” correspond to “up areas” of the chemical embossing, andthe “non-foamed regions correspond to the “down areas” of the chemicalembossing. Although no foaming is preferred in the “down areas” toimpart the deepest chemical embossing effect, some amount of foaming(partial foaming) may occur in the “non-foamed regions” dependent uponchemical embossing conditions. Therefore, “non-foamed regions” alsoinclude partial foamed regions as long as they impart a chemicalembossing effect.

The present method provides for the creation of low gloss/textured grout(nonfoamed or restricted) regions, a higher gloss, and lightly texturedor untextured up regions (foamed regions). The mechanical embossingtexture is substantially set into the wear layer or top coat overlyingthe nonfoamed or restricted portions of the surface covering. Incontrast, the embossing texture is not substantially set into the wearlayer or top coat overlying the foamed portions of the surface coveringcoating.

Additionally, the areas which are highly textured have a lower glossvalue than those which have very little texturing set into the coatinglayer. Although not wishing to be bound by any one theory, it isbelieved that this differential texturing is essentially accomplishedthrough creating a different temperature or heat capacity gradient onthe surface and within the surface covering. The thermal insulationcapabilities of the foam (up regions), versus the nonfoamed orrestricted regions (down areas) provide for different heating andcooling rates due to heat capacity differences. This temperature andheat capacity gradient affects not only the embossability property ofthe wear layer or top coat, but also affects the ability to “set” theembossing texture into the wear layer or top coat once formed under theprocess conditions.

In one embodiment, heating can occur mainly from the bottom (back) ofthe substrate. In this case, the thermal insulation capabilities of thefoamed (up regions), versus the nonfoamed regions (down areas) allowsthe wear layer overlying the non-foamed regions to reach embossingtemperature before the wear layer overlying the foamed regions.Additionally, the thermal insulating properties of the foamed regionsversus the non-foamed or restricted regions also effects the rate ofcooling and “set” of the mechanical embossing texture. This results in aflooring product that has a selectively textured and differentially lowglossed appearance, which creates a more appealing natural visual.

Additionally, in an embodiment a hot drum is used to effectivelytransfer the heat from the back of the covering, and emboss the surfacecovering while it is in contact with the heated drum.

Furthermore, in an additional embodiment the temperature gradient of thesurface covering is adjusted for achieving the selective texturing byincreasing the line speed of a continuous laminate process. The methodcan result in grout lines being selectively textured. In this methodthere is little or no heat loss in the face (wear layer) overlying thegrout regions since they make little to no contact with the “temperingrolls”. Additionally, when the line speed is increased in a continuousprocess, the difference in thermal gradient (back to face) is such thatthe gradient (high backside temperature and heat capacity) can be thecontrolling factor.

Generally, the mechanical and chemical embossing process is illustratedin FIGS. 1 and 3. As illustrated, a web 19 is formed comprising asubstrate 12, a curable wear layer 18, an expandable foam layer 14between the substrate 12 and the wear layer 18, and at least oneinhibitor composition disposed as a pattern proximate the foam layer 14.The wear layer 18 is coated with a cross-linkable top coat 20 to form acoated web 21 and then heated to a temperature at which the top coat 20is substantially cross-linked and cured, the wear layer 18 issubstantially cured, the foam layer 14 substantially expands, and thepattern is chemically embossed to form a surface covering 11.Thereafter, the surface covering 11 is tempered to a temperaturegenerally above ambient temperature. The top coat 20 is then heated ifrequired, and at least one surface texture is mechanically embossed ontothe top coat 20. Upon setting the surface texture, the mechanically andchemically embossed surface covering 10 is formed. In addition,mechanical embossing includes mechanical embossing in register with aprinted or chemically embossed pattern of the surface covering 11.

The expandable foam layer 14 comprises a resinous composition containinga chemical blowing agent and is applied to a surface of the substrate 12to form a coated substrate 13. Preferably, the expandable foam layer 14has a substantially uniform thickness. The expandable foam layer 14 iscoated onto the substrate 12 by any suitable conventional coatingapparatus 28 such as a reverse roll coater, a doctor blade, an airknife, or other similar coating apparatus. The coated substrate 13 isthen passed through a heating unit 30 which supplies sufficient heat toat least partially gel or solidify the thermoplastic resinous coatingwithout decomposing the blowing agent. Any conventional heating unitsuch as a bank of radiant heaters, an oven, a heated drum, and the likemay be utilized. Depending upon the material, the foamable layer canalso be produced by melt processing techniques such as calendering orextrusion.

The gelled foam layer 14 and substrate 12 may then be passed to aprinting unit 32 which places the print layer 16 preferably comprising aprinting ink composition onto the gelled foam layer 14. Any conventionalprinting apparatus such as a silk screen apparatus, a flat bed printingmachine, an ink jet printer, or a conventional gravure or rotogravurepress which is etched to print a design with a suitable ink can beutilized to print on the surface of the gelled foam layer 14. The printlayer 16 is conventionally dried in the printing unit 32. One or more ofthe printing ink compositions, which may be either pigmented ortransparent, contains an inhibitor or an activator for the blowing agentin the foamable layer 14. Further, concentrations of inhibitor oraccelerator can differ from one printing ink composition to another.Accordingly, the print layer 16 can be printed wherein the printing inkand inhibitor or accelerator composition vary from one portion or areato another.

Alternatively, or in addition to the inhibitor or accelerator present inthe print layer 16, the inhibitor or accelerator can be printed orotherwise applied to the substrate 12 and then the foam layer 14 appliedover the inhibitor or accelerator. Accordingly, the inhibitor oraccelerator composition can be a pigmented composition. For example, theprinting ink composition can be visible from the surface of themechanically and chemically embossed surface covering 10. The pigmentedcomposition is visible if substantially complete inhibition of theblowing agent is obtained, and the non-foam areas of the foam layer 14and any subsequent layers disposed thereon are at least translucent orsubstantially clear.

The wear layer 18 comprises a coat of a resinous composition, such as apolyvinyl chloride plastisol or organosol, and is applied over the printor foam layers 16, 14 by another conventional coating apparatus 28 suchas a reverse roll coater, a doctor blade, an air knife, or other similarcoating apparatus. Optionally, the wear layer can also comprise meltprocessable composition such as general purpose, polyvinyl chloride,polyolefin, or other polymers that can be applied by calendering orextrusion, or laminating to the foamable layer. Preferably, the wearlayer 18 has a substantially uniform thickness across the coatedsubstrate 13. The wear layer 18 is preferably transparent, but can betranslucent or pigmented opaque. If the wear layer 18 is opaque, theinks will not be visible from the surface of the mechanically andchemically embossed surface covering 10. After applying the wear layer18, the composite structure is passed through another heating unit 36which supplies sufficient heat to at least partially gel the wear layer18 (if necessary) without decomposing the blowing agent to form a web19. Again, any conventional heating unit such as a bank of infraredheating lamps, an oven, a heated drum, and the like may be utilized.Thereafter, a print layer 16 can be optionally printed onto the gelledwear layer 18 in addition to, or as an alternative to, the print layer16 on the foam layer 14. However, for chemical embossing of the foamlayer 14, an inhibitor and/or accelerator must be able to interact withthe foam layer 14 for the areas in which non-foaming, and/or foaming isdesired.

As previously discussed, the plastisol based foam and wear layers 14, 18are formed into a coating having the desired thickness and then heatedto gel the composition to provide a suitable surface for application ofthe inhibitor, the print layer 16, and/or other layers or coatings. Theterm “gel” includes both the partial solvation to the elastomeric pointof the resinous composition and complete solvation of the resin orresins with the plasticizer to fuse the layers and top coat. Forexample, the temperature is raised to between about 275° F. and about325° F., preferably about 300° F., to gel the polyvinyl chlorideresinous plastisol compositions.

The top coat 20 may then be applied over the wear layer 18 to form thecoated web 21. Preferably, the top coat 20 comprises a coat of across-linkable resinous composition, such as a cross-linkablepolyurethane, epoxies, melamines, and other cross-linkable resins.Thermoplastic resins, such as thermoplastic polyurethane and acrylicscan also be employed. The top coat 20 is applied by another conventionalcoating apparatus 28 such as a reverse roll coater, a doctor blade, anair knife, or other similar coating apparatus to form a coated web.Similar to the wear layer 18, the top coat 20 can be transparent,translucent, or pigmented opaque and, preferably, has a substantiallyuniform thickness across the wear layer 18. Again, if the top coat 20 isopaque, the inks will not be visible from the surface of themechanically and chemically embossed surface covering 10.

The coated web 21 is then passed through a fusion oven 40 to fuse, cure,and expand the coated web 21, thereby forming a surface covering 11. Thefusion oven 40 can be any heating apparatus such as a hot airimpingement oven or infrared heat lamps. Preferably, the fusion oven 40heats both surfaces of the coated web 21. The fusion oven 40 raises thetemperature of the resinous compositions on the substrate 12 high enoughto sufficiently cause the selective decomposition of the blowing agentcontained in the foam layer 14 and to completely solvate and fuse allresinous layers on the substrate 12. If the substrate 12 comprises aresinous composition, the substrate 12 is fused to an adjacent resinouslayer, such as the foam layer 14. The cellular foam areas not in contactwith, or exposed to, any inhibitor composition can reach their maximumexpansion or blow. The portion of foam layer 14 in contact with any areaor composition having a concentration of inhibitor will have little orno foam structure or expansion. However, as indicated above, those foamareas exposed to a portion of the print layer 16 having smallerconcentrations of inhibitor can have more foam structure or expansionthan those areas having a greater concentration of inhibitor.

Upon exiting the fusion oven 40, the surface covering 11 is tempered toat least a temperature where the surface covering 11 resists blisteringor separation between the substrate and layers thereof upon applicationof an external stress, such as a mechanical embossing procedure.Tempering is accomplished in the present invention by temperaturereduction of the surface covering. This is particularly important sinceany premature handling of the surface covering 11 immediately afterfoaming might cause partial collapse and distortion of the foamstructure.

Preferably, the surface temperature of the PVC plastisol wear layeroverlying the foamed regions is reduced to about 240° F. or below andthe wear layer overlying the non-foamed regions is maintained aboveabout 240° F. However, these temperature ranges can vary significantlydepending upon the temperature required to substantially liquefy eitherthe wear layer or top coat overlying the nonfoamed regions, as well asthe temperature gradient difference between the foamed and nonfoamedregions. For example the temperature gradient differences between thefoamed and nonfoamed regions may be such that the surface temperature ofthe wear layer and top coat overlying both regions may be the same. Theterm “substantially liquefy” or “substantially fluid” is meant toinclude any state in which either the wear layer or top coat can bemechanically embossed with a surface texture and that such texture iscapable of being set into either the wear layer or the top coat upon thecooling of the surface covering by the embossing roll. Of course, theexact ranges of temperatures will also vary depending upon thecomposition comprising either the wear layer or top coat.

Tempering the surface covering to the desired temperature reduces energydemands by forgoing an additional heating step before mechanicalembossing. Thus, this embodiment permits a continuous process whichreduces handling requirements by the manufacturer, and reduces spacerequirements for either storage or process line length. In anotherembodiment, the chemical embossed surface covering is cooled to ambientconditions and subsequently reheated, temperature gradients adjusted,and mechanically embossed resulting in the same desired effect.

Tempering can be accomplished through various methods such as byallowing the surface covering to sufficiently cool to the desiredtemperature through atmospheric radiant heat transfer as it moves alongthe process line prior to engaging any device following the fusion oven.A blowing device (not shown), such as a fan or an air conditioning unit,may be employed to assist in this tempering technique. Preferably, atempering unit 42 is utilized to temper the surface covering. Dependingupon line speed, surface covering composition, and surface coveringtemperature exiting the fusion oven 40, a conventional back wetter 46may be included.

As illustrated, the tempering unit 42 can comprise at least one surfacecooled tempering roller 44 having a relatively smooth contact surface.The tempering unit 42 has two water-cooled, chrome-plated steeltempering rollers 44. The tempering rollers 44 are preferably to onlycome in contact with the wear layer or top coat which resides over thefoamed portions of the surface covering. FIG. 1 illustrates thetempering rollers 44 positioned so that the surface covering 11 is fedthrough the tempering rollers in an “S” configuration and passes aroundand is maintained in contact with between from about 180° to about 200°of the circumference of each tempering roller 44 (about 180° to about200° of wrap). In this configuration, the substrate 12 of the surfacecovering 11 initially contacts one tempering roller 44, and the othertempering roller 44 contacts the top coat 20 residing over the foamedregions of the surface covering. Preferably, the tempering roller incontact with the wear layer will be significantly cooler than thetempering roll in contact with the substrate.

To avoid incidental mechanical embossing of the top coat 20, thetempering roller 44 contacting the top coat 20 should have a surfaceroughness no greater than 32 microinch (10⁻⁶ inch) root-mean squared (32RMS). The surface smoothness of the tempering roller 44 contacting thesubstrate 12 is not as critical. Clearly, the tempering rollers 44 canhave any desired outside diameter, more than two tempering rollers 44may be utilized, and the amount of wrap about the tempering rollers 44can be more or less than that mentioned above.

In a further embodiment, the surface covering can be heated by a heater50 which rapidly heats the top coat 20 after tempering. Importantly, thetop coat 20 residing over the nonfoamed regions should be heated to asufficient degree to allow it to be mechanically embossed withoutfracture, cracking, or structural failure, such as de-lamination. Thatis, the top coat 20 is heated to a sufficient temperature for asufficient time in order to soften or even further soften the top coat20.

The amount of heat (if any) to be applied and the duration of suchapplication depends upon, among other things, the temperature gradientof the surface covering 11 exiting the tempering unit 42, thecomposition of the top coat 20, the thickness of the top coat 20, thespeed of the moving surface covering 11, the color of the printed designunder the wear layer 18 surface, and the color of the resinous layers.To further enhance heating of the top coat 20, the resinous layers cancomprise a resin or contain agents which absorb energy from a desiredfrequency of the infrared spectrum.

Optionally, the high temperature heater 50 may be a burner, such as agas burner. One example is the “Blu-Surf” burner sold by the Blu-SurfDivision of Hayes-Albion Corporation of Parma, Mich. This is a burnerwhich operates with a very short flame coming off an air-gas manifold.The hot gases from the flame are directed by a nozzle structure towardsthe top coat of the surface covering.

Preferably, the high temperature heater 50 comprises a bank of infraredheaters. Suitable infrared heaters are 10.1 kW RADPLANE SERIES 81infrared heaters manufactured by Glenro, Inc., Patterson, N.J. The hightemperature heater 50 should extend beyond the respective edges of thesurface covering 11 to assist in heating the portions of the top coat 20proximate the edges. Top coat edge temperature and heating are furtherdiscussed below.

In a further embodiment, the surface covering is heated from thebackside. The backside of the surface covering is that side having theexposed substrate or the side opposite the applied top coat or wearlayer. Heat is applied to the backside of the surface covering to createa temperature gradient such that the substrate has a temperature whichis greater than the top coat or wear layer of the surface covering. Thetemperature of the substrate is such that there is a difference in wearlayer/top coat temperature gradient overlying the foamed and non-foamedregions. By heating the backside of the surface covering, varyingdegrees of temperature gradient can be achieved in the top coat, sincethe foamed regions have an insulation value which retards the transferof heat from the heated substrate to the top coat overlying the foamedregions. The reverse is true for the top coat overlying the nonfoamedregions, where heat can be more directly transferred to the top coatoverlying the nonfoamed regions.

The backside of the surface covering can be heated by any conventionalmeans described above. Such means can include, but is not limited to,passing the backside of the surface covering over a heated drumconventionally used in the surface covering industry. Additionally,infrared heaters or other heat sources may be utilized.

Mechanical embossing can comprise a conventional engraved steelembossing roll 54 and a back-up roll 56. Preferably, the embossing roll54 is water cooled and servo-driven, and the back-up roll is a steelback-up roll 56. Upon engaging the embosser nip 52, the steel back-uproll 56 contacts the substrate 12 and the embossing roll 54 contacts thehot top coat 20 of the surface covering 11.

Preferably, the embossing roll 54 has substantially the same temperatureacross its surface. This contact with the cooled embossing roll surfaceremoves heat from the top coat 20 of the surface covering 11 by heattransfer from the surface covering 11 to the water-cooled, steelembossing roll 54, and thus “sets” the embossing substantially in thenonfoamed regions of the surface covering, such as in the grout lines.In addition to setting the embossed texture substantially in thenonfoamed regions, a differential gloss pattern is also set onto the topcoat or wear layer. The level of gloss is lower in the embossed regionsthan in the non-embossed regions or the foamed regions. Dwell time ofthe surface covering on the embossing roll 54 is dependent on exactembossing roll circumference, wrap, and line speed, which can bedetermined by one skilled in the art.

The embosser nip 52 or gap can float against a fixed pressure or,preferably, be adjustably fixed. Adjustment to the embosser nip 52 canbe made, for example, by adjustable steel wedge blocks (not shown) or,preferably, by a jack screw (not shown). However, when the embosser nip52 is fixed, consistent caliper of the surface covering 11 prior toentry into the mechanical embossing section of the process needs to bemonitored and maintained.

During mechanical embossing, the embossing roll 54 can be bottomed outagainst the top coat surface. Not only the raised areas, but also thedepressed areas of the embossed pattern on the embossing roll 54substantially engage the top coat 20 of the surface covering 11.Consequently, both the raised and depressed areas of the embossing roll54 can initially provide a pattern effect directly on both the foamedand nonfoamed regions of the top coat 20 of the surface covering 11.However, upon the setting of the surface texture, only the texture thathas been embossed over the nonfoamed regions sets substantially.

The mechanically and chemically embossed surface covering 10 then passesto a tension control device 60, such as a dancer structure, a load cellroll, and the like, which maintains tension control in the process line,particularly the mechanical embossing section. At about this point, themechanically and chemically embossed surface covering 10 has been cooledto between approximately 75° F. and approximately 100° F. (ambienttemperature). The mechanically embossed texture is then setsubstantially over the nonfoamed regions of the surface covering. Ofcourse, varying degrees of texture can also be applied and set onto thefoamed regions, but such a texture would not be set onto the foamedregions with the same degree as the texture set onto the nonfoamedregions.

The following examples are intended to illustrate the invention and itis thought variations will occur to those skilled in the art.Accordingly, it is intended that the scope of the invention should belimited only by the appended claims.

EXAMPLES Example 1

In Example 1, there is illustrated a mechanically and chemicallyembossed surface covering having a wear layer which is mechanicallyembossed predominantly over the non-foamed regions.

A felt substrate having a thickness of approximately 10 mils was coatedwith a substantially uniform coat of a polyvinyl chloride HMC (hot meltcalendered) layer having a depth of approximately 25 mils and applied bya calender. The substrate and HMC layer were tempered to approximately75° F. An expandable foam layer of a polyvinyl chloride plastisolcontaining a blowing agent is applied with a blade coater. Theexpandable foam layer has a wet applied average thickness of about 10mils.

Thereafter, the expandable foam layer was gelled to a relatively firmcondition by heating the foam layer to a temperature of approximately300° F. for approximately 6 seconds. In this example, the foam layer washeated without expanding the foam layer. A print ink compositioncontaining an inhibitor composition was printed and dried on the gelledexpandable foam layer by a conventional rotogravure printing apparatusto form a print layer. The print layer may be printed in a grout patterndesign.

A clear, non-foaming polyvinyl chloride plastisol wear layer having anapplied thickness of approximately 10 mils was then coated onto theprint layer by a blade coater to form the coated web. The coated web waspassed through a fusion oven at a temperature of approximately 400° F.for approximately 50 seconds to expand and cure the foam layer, cure thewear layer, cure the top coat, and fuse all resinous layers to form asurface covering. The portions of the foamable layer in contact with thegrout-printed pattern of the print layer do not expand, therebychemically embossing the printed pattern into the foam layer. Uponexiting the fusion oven, the surface covering was tempered by passingthe surface covering in an “S” configuration between two water cooledtempering rollers, with a wrap on each tempering roller of approximately180°. The line conditions were such that the surface of the nonfoamedregions or the grout/down areas made minimum or no contact with thetempering rollers. The temperature of the tempering rollers iscontrolled to provide a top surface temperature of about 255° F. and abottom temperature of about 292° F.

Subsequently, the surface covering entered the embosser nip. Theembosser nip was formed by the water-cooled, chrome-plated steelembosser roll having an overall pattern on the surface thereof and thechrome plated steel back-up roll, with a gap of approximately 42 mils.Upon entering the embosser nip, the pattern of the embossing rollmechanically came in contact with the surface of the product. Thetemperature profile and heat transfer properties of the product weresuch that embossing only occurs in the wear layer surface overlying thenonfoamed regions or grout regions. The embossing roll surfacetemperature is maintained at approximately 80° F., thereby setting themechanically embossed pattern and forming the mechanically andchemically embossed surface covering.

Additionally, the temperature of the wear layer surface exiting the IRoven can be raised, or the line speed can be decreased (longer dwelltime/more heat transfer) to add some degree of texturing to the foamedregions or the up areas. But the majority of the texturing still occursin the nonfoamed regions.

Upon cooling to ambient temperature, the mechanically and chemicallyembossed surface covering was found to be acceptably and permanentlyembossed in the grout regions.

Example 2

In Example 2, there is illustrated a similar process as illustrated inExample 1, except a top coat was further applied to the mechanically andchemically embossed surface covering having a wear layer.

The top coat of a cross-linkable polyurethane-melamine resin having awet applied thickness of approximately 1 mil was coated onto the gelledwear layer by a reverse roll coater to form a coated web. The coated webwas processed similar to that in Example 1. The line speed and heatingprofiles were controlled similar to that in Example 1, resulting in afinal product structure having a top coat embossed only in groutregions.

Example 3

A flooring product of similar composition to that of Example 1 isprocessed through the same process as described, except that radiantheaters 50′ are positioned under the backing so that heat is applied tothe product from the back side. Heat is thermally conducted through theconstruction such that the surface temperature of wear layer overlyingthe nonfoamed (chemically embossed down) regions rises faster than thesurface temperature of the wear layer overlying the thermally insulatingfoamed (chemically embossed up) regions. When the temperature of thewear layer overlying the nonfoamed regions reaches an embossable, fluidstate, the product is passed through the embossing nip (overallpatterned embossing roll). The resultant product upon cooling exhibits atextured grout (down) region with no texture on the up regions. Ifradiant heat is also simultaneously applied to the top surface, theconditions of the process can be varied such that a slight or differenttexture is obtained on the up areas while a strong texture is obtainedin the grout regions.

Example 4

The backing layer of a chemically embossed flooring product of similarcomposition to that of Example 1 is brought into contact with a heateddrum after the tempering rolls. The drum is configured with an overallpatterned embossing roll down stream from where the flooring productmakes first contact with the drum. The temperature and dwell time on thedrum is adjusted such that the temperature of the wear layer over thenonfoamed (CE down) regions rises and reaches an embossable fluid state,and the temperature of the wear layer over the foamed (CE up) regionsdoes not rise sufficiently to reach an embossable state.

Subsequently, the product is contacted by a mechanical embossing rollsimilar to that in U.S. Pat. No. 5,961,903, which textures the surfaceof the grout (CE down) regions while not texturing the other surfaces ofthe product. The resulting visual effect is that of a lowergloss-textured grout region that realistically simulates a groutedceramic tile visual. Radiant heat can be added to the surface to providethe ability to strongly texture the grout regions and slightly texturethe wear layer overlying the foamed regions.

While specific embodiments have been set forth as illustrated anddescribed above, it is recognized that variations may be made withrespect to disclosed embodiments. Therefore, while the invention hasbeen disclosed in various forms only, it will be obvious to thoseskilled in the art that many additions, deletions and modifications canbe made without departing from the spirit and scope of this invention,and no undue limits should be imposed except as set forth in thefollowing claims.

1. A method of manufacturing an embossed surface covering comprising:forming a surface covering comprising a wear layer overlying a foamlayer, said foam layer having a foamed region and a substantiallynon-foamed region; adjusting the temperature of the formed surfacecovering such that a temperature gradient exists laterally across thewear layer between the region of the wear layer substantially overlyingthe foamed region and the region of the wear layer substantiallyoverlying the non-foamed region; and thereafter, mechanically embossingthe wear layer whereby a surface texture is set predominantly into thewear layer substantially overlying the non-foamed region.
 2. The methodof claim 1, wherein the foamed region and non-foamed region areselectively disposed in accordance with a predetermined pattern.
 3. Themethod of claim 1, wherein the surface covering further comprises asubstrate underlying the foam layer and a chemical foaming inhibitor oractivator is selectively disposed proximate the foam layer.
 4. Themethod of claim 1, wherein the surface temperature of the wear layersubstantially overlying the non-foamed region is higher than the surfacetemperature of the wear layer substantially overlying the foamed regionprior to the mechanical embossing step.
 5. The method of claim 1,wherein the surface covering has a back-side opposite the wear layer andthe surface temperature of the back-side of the surface covering ishigher than the surface temperature of the wear layer prior to themechanical embossing step.
 6. The method of claim 5, wherein heat isapplied to the back-side of the surface covering to adjust thetemperature gradient.
 7. The method of claim 6, wherein the back-side ofthe surface covering is heated with a heated drum.
 8. The method ofclaim 6, wherein the back-side of the surface covering is heated suchthat the wear layer substantially overlying the non-foamed region issubstantially fluid and the wear layer substantially overlying thefoamed region is not substantially fluid.
 9. The method of claim 1,wherein the temperature gradient is adjusted by tempering the surfacecovering before the mechanical embossing step.
 10. The method of claim9, wherein the surface covering is tempered with a smooth surfaced roll.11. The method of claim 10, wherein the smooth surfaced roll engages thewear layer predominantly overlying only the foamed region of the surfacecovering.
 12. The method of claim 1, wherein the surface covering iscooled to ambient temperature before adjusting the temperature gradient.13. The method of claim 1, further including heating the wear layer ofthe surface covering before the mechanical embossing step.
 14. Themethod of claim 1, further comprising mechanically embossing a surfacetexture into the wear layer predominantly overlying the foamed regionsuch that the set surface texture overlying the foamed region isdifferent than the set surface texture overlying the non-foamed region.15. The method of claim 14, wherein surface texture is set into the wearlayer overlying the foamed region to a lesser extent than the surfacetexture set into the wear layer overlying the non-foamed region.
 16. Themethod of claim 14, wherein the surface texture is achieved with anembossing tool having a plurality of regions of different texture. 17.The method of claim 14, wherein a surface texture is mechanicallyembossed into the wear layer substantially overlying the foamed regionand into the wear layer substantially overlying the non-foamed region inseparate processing steps and wherein a first temperature gradient isestablished prior to a first mechanical embossing step and a secondtemperature gradient is established prior to a second mechanicalembossing step.
 18. The method of claim 3, wherein the substrate furthercomprises a melt processed resin layer.
 19. The method of claim 18,wherein the melt processed resin layer is hot melt calendered.
 20. Themethod of claim 18, wherein the melt processed resin layer comprises aresin selected from the group consisting of polyvinyl chloride,polyethylene, polypropylene, polystyrene, metallocene polyolefin, andcopolymers thereof.
 21. The method of claim 1, wherein the wear layer isa plastisol or an organosol composition comprising a resin selected fromthe group consisting of a homopolymer of polyvinyl chloride, a copolymerof polyvinyl chloride, and combinations thereof.
 22. The method of claim1, wherein the wear layer comprises a melt processed resin layer. 23.The method of claim 22, wherein the melt processed resin layer comprisesa resin selected from the group consisting of a polyvinyl chloridehomopolymer, a polyvinyl chloride copolymer, a polyamide, a polyester, apolyolefin homopolymer, a polyolefin copolymer, an acrylic resin, andcombinations thereof.
 24. The method of claim 1, wherein the foam layercomprises a plastisol or organosol composition comprising a resinselected from the group consisting of a homopolymer of polyvinylchloride, a copolymer of polyvinyl chloride, and combinations thereof.25. The method of claim 1, wherein the foam layer comprises a meltprocessed resin.
 26. The method of claim 25, wherein the melt processedresin layer comprises a resin selected from the group consisting of apolyvinyl chloride homopolymer, a polyvinyl chloride copolymer, apolyamide, a polyester, a polyolefin homopolymer, a polyolefincopolymer, an acrylic resin, and combinations thereof.
 27. The method ofclaim 1, wherein the wear layer substantially overlying the non-foamedregion has a lower gloss value than the gloss value of the wear layersubstantially overlying the foamed region.
 28. The method as in any oneof the preceding claims, wherein the wear layer is a composite layercomprising a plurality of strata and wherein the uppermost stratacomprises a topcoat.
 29. The method of claim 2, wherein the wear layeris a composite layer comprising a plurality of strata and wherein theuppermost strata comprises a topcoat; and wherein the topcoat comprisesa cross-linked resinous composition.
 30. A method of manufacturing anembossed surface covering comprising: forming a web comprising asubstrate, a foamable layer, and at least one chemical foaming inhibitoror activator composition disposed proximate the foamable layer inaccordance with a predetermined pattern; coating the web with acomposite wear layer comprising a plurality of strata including anuppermost strata comprising a cross-linkable topcoat; heating thecomposite wear layer coated web to a temperature at which the wear layeris cured and the foamable layer is selectively expanded such that thefoamable layer forms a foam layer having a foamed region and asubstantially non-foamed region in accordance with the predeterminedpattern; adjusting the temperature of the wear layer coated expanded websuch that a temperature gradient exists laterally across the wear layerbetween the region of the wear layer substantially overlying the foamedregion and the region of the wear layer substantially overlying thenon-foamed region; and thereafter, mechanically embossing the wear layerwhereby a surface texture is set predominantly into the wear layersubstantially overlying the non-foamed region.